--- a/services/sync/tps/extensions/mozmill/resource/driver/controller.js
+++ b/services/sync/tps/extensions/mozmill/resource/driver/controller.js
@@ -61,17 +61,17 @@ waitForEvents.prototype = {
 
   /**
    * Wait until all assigned events have been fired
    */
   wait: function waitForEvents_wait(timeout, interval) {
     for (var e in this.registry) {
       assert.waitFor(function () {
         return this.node.firedEvents[e] == true;
-      }, "waitForEvents.wait(): Event '" + ex + "' has been fired.", timeout, interval);
+      }, "waitForEvents.wait(): Event '" + e + "' has been fired.", timeout, interval);
 
       this.node.removeEventListener(e, this.registry[e], true);
     }
   }
 }
 
 /**
  * Class to handle menus and context menus
@@ -788,17 +788,17 @@ MozMillController.prototype.assertImageL
   }
 
   var comp = img.complete;
   var ret = null; // Return value
 
   // Workaround for Safari -- it only supports the
   // complete attrib on script-created images
   if (typeof comp == 'undefined') {
-    test = new Image();
+    let test = new Image();
     // If the original image was successfully loaded,
     // src for new one should be pulled from cache
     test.src = img.src;
     comp = test.complete;
   }
 
   // Check the complete attrib. Note the strict
   // equality check -- we don't want undefined, null, etc.
@@ -977,19 +977,19 @@ function browserAdditions (controller) {
     }
     catch (ex) {
       if (!(ex instanceof errors.TimeoutError)) {
         throw ex;
       }
       timed_out = true;
     }
     finally {
-      state = 'URI=' + win.document.location.href +
+      let state = 'URI=' + win.document.location.href +
               ', readyState=' + win.document.readyState;
-      message = "controller.waitForPageLoad(" + state + ")";
+      let message = "controller.waitForPageLoad(" + state + ")";
 
       if (timed_out) {
         throw new errors.AssertionError(message);
       }
 
       broker.pass({'function': message});
     }
   }

--- a/services/sync/tps/extensions/mozmill/resource/driver/elementslib.js
+++ b/services/sync/tps/extensions/mozmill/resource/driver/elementslib.js
@@ -339,18 +339,18 @@ var _byName = function (_document, paren
 }
 
 var _byAttrib = function (parent, attributes) {
   var results = [];
   var nodes = parent.childNodes;
 
   for (var i in nodes) {
     var n = nodes[i];
-    requirementPass = 0;
-    requirementLength = 0;
+    let requirementPass = 0;
+    let requirementLength = 0;
 
     for (var a in attributes) {
       requirementLength++;
       try {
         if (n.getAttribute(a) == attributes[a]) {
           requirementPass++;
         }
       } catch (e) {

--- a/services/sync/tps/extensions/mozmill/resource/driver/mozmill.js
+++ b/services/sync/tps/extensions/mozmill/resource/driver/mozmill.js
@@ -235,17 +235,17 @@ function getAddrbkController () {
   if (addrbkWindow == null) {
     return newAddrbkController();
   } else {
     return new controller.MozMillController(addrbkWindow);
   }
 }
 
 function firePythonCallback (filename, method, args, kwargs) {
-  obj = {'filename': filename, 'method': method};
+  let obj = {'filename': filename, 'method': method};
   obj['args'] = args || [];
   obj['kwargs'] = kwargs || {};
 
   broker.sendMessage("firePythonCallback", obj);
 }
 
 function timer (name) {
   this.name = name;

--- a/services/sync/tps/extensions/mozmill/resource/modules/assertions.js
+++ b/services/sync/tps/extensions/mozmill/resource/modules/assertions.js
@@ -92,17 +92,17 @@ Assert.prototype = {
     //~~~I've managed to break Object.keys through screwy arguments passing.
     // Converting to array solves the problem.
     if (isArguments(a)) {
       if (!isArguments(b)) {
         return false;
       }
       a = pSlice.call(a);
       b = pSlice.call(b);
-      return _deepEqual(a, b);
+      return this._deepEqual(a, b);
     }
     try {
       var ka = Object.keys(a),
           kb = Object.keys(b),
           key, i;
     } catch (e) {//happens when one is a string literal and the other isn't
       return false;
     }
@@ -391,17 +391,18 @@ Assert.prototype = {
    * @throws {errors.AssertionError}
    *
    * @returns {boolean} Result of the test.
    */
   match: function Assert_match(aString, aRegex, aMessage) {
     // XXX Bug 634948
     // Regex objects are transformed to strings when evaluated in a sandbox
     // For now lets re-create the regex from its string representation
-    let pattern = flags = "";
+    let pattern = "";
+    let flags = "";
     try {
       let matches = aRegex.toString().match(/\/(.*)\/(.*)/);
 
       pattern = matches[1];
       flags = matches[2];
     } catch (e) {
     }
 

--- a/services/sync/tps/extensions/mozmill/resource/modules/frame.js
+++ b/services/sync/tps/extensions/mozmill/resource/modules/frame.js
@@ -280,17 +280,17 @@ events.fail = function (obj) {
     };
   }
 
   // a low level event, such as a keystroke, fails
   if (events.currentTest) {
     events.currentTest.__fails__.push(obj);
   }
 
-  for (var time of timers) {
+  for (var timer of timers) {
     timer.actions.push(
       {"currentTest": events.currentModule.__file__ + "::" + events.currentTest.__name__,
        "obj": obj,
        "result": "fail"}
     );
   }
 
   events.fireEvent('fail', obj);

--- a/services/sync/tps/extensions/mozmill/resource/modules/l10n.js
+++ b/services/sync/tps/extensions/mozmill/resource/modules/l10n.js
@@ -19,17 +19,17 @@ Cu.import("resource://gre/modules/Servic
  * @returns {String} Localized content
  */
 function getEntity(aDTDs, aEntityId) {
   // Add xhtml11.dtd to prevent missing entity errors with XHTML files
   aDTDs.push("resource:///res/dtd/xhtml11.dtd");
 
   // Build a string of external entities
   var references = "";
-  for (i = 0; i < aDTDs.length; i++) {
+  for (let i = 0; i < aDTDs.length; i++) {
     var id = 'dtd' + i;
     references += '<!ENTITY % ' + id + ' SYSTEM "' + aDTDs[i] + '">%' + id + ';';
   }
 
   var header = '<?xml version="1.0"?><!DOCTYPE elem [' + references + ']>';
   var element = '<elem id="entity">&' + aEntityId + ';</elem>';
   var content = header + element;
 

--- a/services/sync/tps/extensions/mozmill/resource/stdlib/objects.js
+++ b/services/sync/tps/extensions/mozmill/resource/stdlib/objects.js
@@ -1,17 +1,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, you can obtain one at http://mozilla.org/MPL/2.0/. */
 
 var EXPORTED_SYMBOLS = ['getLength', ];//'compare'];
 
 var getLength = function (obj) {
   var len = 0;
-  for (i in obj) {
+  for (let i in obj) {
     len++;
   }
 
   return len;
 }
 
 // var logging = {}; Components.utils.import('resource://mozmill/stdlib/logging.js', logging);
 

--- a/services/sync/tps/extensions/mozmill/resource/stdlib/securable-module.js
+++ b/services/sync/tps/extensions/mozmill/resource/stdlib/securable-module.js
@@ -86,17 +86,17 @@
    function maybeParentifyFilename(filename) {
      var doParentifyFilename = true;
      try {
        // TODO: Ideally we should just make
        // nsIChromeRegistry.wrappersEnabled() available from script
        // and use it here. Until that's in the platform, though,
        // we'll play it safe and parentify the filename unless
        // we're absolutely certain things will be ok if we don't.
-       var filenameURI = ios.newURI(options.filename,
+       var filenameURI = ios.newURI(filename,
                                     null,
                                     baseURI);
        if (filenameURI.scheme == 'chrome' &&
            filenameURI.pathQueryRef.indexOf('/content/') == 0)
          // Content packages will always have wrappers made for them;
          // if automatic wrappers have been disabled for the
          // chrome package via a chrome manifest flag, then
          // this still works too, to the extent that the